The extremal limits of the C-metric: Nariai, Bertotti-Robinson and anti-Nariai C-metrics

In two previous papers we have analyzed the C-metric in a background with a cosmological constant, namely the de Sitter (dS) C-metric, and the anti-de Sitter (AdS) C-metric, following the work of Kinnersley and Walker for the flat C-metric. These exact solutions describe a pair of accelerated black holes in the flat or cosmological constant background, with the acceleration A being provided by a strut in-between that pushes away the two black holes. In this paper we analyze the extremal limits of the C-metric in a background with generic cosmological constant. We follow a procedure first introduced by Ginsparg and Perry in which the Nariai solution, a spacetime which is the direct topological product of the 2-dimensional dS and a 2-sphere, is generated from the four-dimensional dS-Schwarzschild solution by taking an appropriate limit, where the black hole event horizon approaches the cosmological horizon. Similarly, one can generate the Bertotti-Robinson metric from the Reissner-Nordstrom metric by taking the limit of the Cauchy horizon going into the event horizon of the black hole, as well as the anti-Nariai by taking an appropriate solution and limit. Using these methods we generate the C-metric counterparts of the Nariai, Bertotti-Robinson and anti-Nariai solutions, among others. One expects that the solutions found in this paper are unstable and decay into a slightly non-extreme black hole pair accelerated by a strut or by strings. Moreover, the Euclidean version of these solutions mediate the quantum process of black hole pair creation, that accompanies the decay of the dS and AdS spaces

Analysis of a General Family of Regularized Navier-Stokes and MHD Models

We consider a general family of regularized Navier-Stokes and Magnetohydrodynamics (MHD) models on n-dimensional smooth compact Riemannian manifolds with or without boundary, with n greater than or equal to 2. This family captures most of the specific regularized models that have been proposed and analyzed in the literature, including the Navier-Stokes equations, the Navier-Stokes-alpha model, the Leray-alpha model, the Modified Leray-alpha model, the Simplified Bardina model, the Navier-Stokes-Voight model, the Navier-Stokes-alpha-like models, and certain MHD models, in addition to representing a larger 3-parameter family of models not previously analyzed. We give a unified analysis of the entire three-parameter family using only abstract mapping properties of the principle dissipation and smoothing operators, and then use specific parameterizations to obtain the sharpest results. We first establish existence and regularity results, and under appropriate assumptions show uniqueness and stability. We then establish results for singular perturbations, including the inviscid and alpha limits. Next we show existence of a global attractor for the general model, and give estimates for its dimension. We finish by establishing some results on determining operators for subfamilies of dissipative and non-dissipative models. In addition to establishing a number of results for all models in this general family, the framework recovers most of the previous results on existence, regularity, uniqueness, stability, attractor existence and dimension, and determining operators for well-known members of this family.Comment: 37 pages; references added, minor typos corrected, minor changes to revise for publicatio

Overstapseizoen 2022-2023: helft van de overstappers geeft aan te wisselen van zorgverzekeraar omdat ze ontevreden zijn over de hoogte van de premie.

Van de verzekerden in Nederland geeft 14% aan te zijn gewisseld van zorgverzekeraar in het overstapseizoen 2022-2023A. Dit percentage is vergelijkbaar met dat van vorig jaar, en hoger dan in de jaren daarvoor (7-10%). Verzekerden in de leeftijdsgroep 18 t/m 39 jaar geven in 2022-2023, zoals elk jaar, vaker aan (25%) te zijn gewisseld dan verzekerden van 40 t/m 64 jaar (10%) en verzekerden van 65 jaar en ouder (4%)

8% van de verzekerden geeft aan te zijn overgestapt van zorgverzekeraar in 2019.

In 2019 geeft 8% van de verzekerden aan te zijn overgestapt van zorgverzekeraar. Dit percentage is vergelijkbaar met dat van de afgelopen jaren. Verzekerden van 18 tot en met 39 jaar geven, in vergelijking met verzekerden van 40 jaar en ouder, vaker aan te zijn overgestapt in 2019. Net als in vorige jaren is de hoogte van de premie de meest genoemde reden om over te stappen van zorgverzekeraar. Tevredenheid over de dekking van de polis is de meest genoemde reden om bij de huidige zorgverzekeraar te blijven. Het percentage verzekerden dat aangeeft aanvullend verzekerd te zijn daalt in 2019 naar 85%. Een merendeel van de verzekerden geeft aan collectief te zijn verzekerd. De keuze voor een vrijwillig eigen risico van €500 is favoriet onder verzekerden in 2019, 12% van de verzekerden kiest hiervoor. De resultaten beschreven in dit factsheet zijn gebaseerd op de antwoorden van 715 respondenten (respons 48%), die lid zijn van het Consumentenpanel Gezondheidzorg van het Nivel

Measuring health insurance literacy in the Netherlands – first results of the HILM-NL questionnaire.

Background There are several indications that citizens in the Netherlands struggle to make critical, well-considered decisions about which insurance policy best fits their needs and preferences. This can lead to citizens being sub-optimally insured, facing unexpected costs or suffering inadequate coverage. This study aims to examine how health insurance literacy (HIL) is distributed among citizens in the Netherlands; and to find out whether there are certain groups who have more difficulty choosing and using a health insurance policy. Methods We measured health insurance literacy using the HILM-NL questionnaire, the validated Dutch version of the original health insurance literacy measure (HILM). In February 2020, the HILM-NL was sent to 1,500 members of the Nivel Dutch Health Care Consumer Panel. The response rate was 54% (806). Results There is a wide variation in HIL among citizens in the Netherlands. The average total HILM-NL score is 55.14 (on a range of 21-84). The level of education and the household net income are significantly related to HIL. Conclusions Citizens who completed less education or earn a lower income are relatively more likely to have difficulty choosing a health insurance policy or using policy benefits to pay for health services once enrolled. It is important to support these vulnerable groups properly in their choice and use of a health insurance policy